Effect of radiation losses on very lean methane/air flames propagating upward in a vertical tube

The stationary upward propagation of a very lean methane/air flame in a long vertical tube open at the bottom and closed at the top is simulated numerically using a single overall chemical reaction to model combustion and assuming an optically thin gas and a transparent or non-reflecting tube wall to approximately account for radiation losses from CO₂${\text{CO}}_2$ and H₂O${\text{H}}_2\text{O}$. Buoyancy plays a dominant role in the propagation of these flames and causes a large region of low velocity of the burnt gas relative to the flame to appear below the flame front when the equivalence ratio is decreased. The size of this region scales with the radius of the tube, and its presence enhances the effect of radiation losses, which would be otherwise negligible for a standard flammability tube, given the small concentration of radiating species. Heat conduction is found to be important in the low velocity region and to lead to a conduction flux from the flame to the burnt gas that causes extinction at the flame tip for a value of the equivalence ratio near the flammability limit experimentally measured in the standard tube. The effect of radiation losses decreases with the radius of the tube. Numerical results and order-of-magnitude estimates show that, in the absence of radiation, a very lean flame front fails to propagate only after recirculation of the burnt gas extends to its reaction region and drastically changes its structure. This condition is not realized for the standard flammability tube, but it seems to account for the flammability limit measured in a tube of about half the radius of the standard tube.     

UPTAKE OF METAL IONS BY A NEW CHELATING ION EXCHANGE RESIN. PART 3: PROTONATION CONSTANTS VIA POTENTIOMETRIC TITRATION AND SOLID STATE 31P NMR SPECTROSCOPY

Abstract

A new chelating ion exchange resin which incorporates methylenediphosphonate, carboxylate, and sulfonate functional groups in a polystyrene-divinylbenzene matrix has been prepared. This resin exhibits exceptionally high affinity for polyvalent cations even from moderately acidic aqueous media. Metal ion coordination occurs primarily at the diphosphonate group with the secondary binding sites contributing to charge neutralization when necessary and possible, and to increasing hydrophilicity of the resin pores. In the present investigation, the protonation equilibria of the phosphonate groups in the resin are investigated via potentiometric titration and solid-state ³¹P NMR spectroscopy of the resin. Intrinsic equilibrium constants for the first two diphosphonate protonation reactions are pk₄7equal; 10.47 and pK₃ = 7.24. The last two protons added to the diphosphonate group are acidic having pK_a values less than 2.5. These protonation constants are consistent with those reported previously for monomer analog 1,1-diphosphonic acids. This result implies that thermodynamic data available in the literature can be used to predict the relative affinity of the resin for polyvalent cations.     

Activation of the haemostatic system in children with juvenile rheumatoid arthritis correlates with disease activity

Twenty-four children with juvenile rheumatoid arthritis (JRA) and 10 children with postinfectious arthropathies were investigated for markers of blood coagulation and fibrinolytic activity: Prothrombin fragment 1+2 (F1+2), thrombin-antithrombin complex (TAT), and D-Dimer were measured using solid phase enzyme linked immunosorbent assays (ELISA). Results were compared with clinical and conventional laboratory signs of disease activity. F1+2, TAT, D-Dimer, and fibrinogen were significantly elevated in children with JRA as compared with healthy children and children with postinfectious arthropathies. F1+2, TAT, and D-Dimer correlated significantly with disease activity, assessed by determination of the joint index score and C-reactive protein (CRP). The study demonstrates a subclinical activation of the haemostatic system in children with JRA correlating with disease activity, which might be caused by the action of several immunomediators on cells (monocytes, endothelial cells) playing a role in the regulation of blood coagulation activity.     

An Eulerian approach for partitioned fluid–structure simulations on Cartesian grids

This paper describes an Eulerian approach for partitioned fluid–structure simulations based on a fluid solver using regularly and adaptively refined Cartesian grids. The particular focus is on the efficient implementation and embedding of the fluid solver in the context of coupled simulations. Special subjects are the efficient layout of data structures and data access based on space-filling curves and the realisation of geometry and topology changes. In addition, a coupling environment is presented that allows for an easy and flexible coupling of flow and structure codes. Simulation results are provided for large particle movements within the drift ratchet scenario.     

Reliability-oriented ant colony optimization-based mobile peer-to-peer VoD solution in MANETs

Mobile peer-to-peer (MP2P) has emerged as a state-of-the-art technology for video resource sharing in mobile ad-hoc networks (MANETs), building on the advantages of P2P data exchange and providing a feasible solution for large-scale deployment of media streaming services. Fast search for video resources and low maintenance overhead of overlay networks to support the mobility of nodes are key factors in MP2P video on demand solutions. In this paper, we propose a novel reliability-oriented ant colony optimization (ACO)-based MP2P solution to support interactivity for video streaming in MANETs (RACOM). RACOM makes use of highly innovative algorithms such as the peer status-aware mechanism and peer-centric overlay maintenance mechanism to support high-efficiency video resource sharing. The peer status-aware mechanism includes the user reliability measure model which is used to identify the peers having reliable playback status in order to find stable potential resource suppliers and a new ACO-based prediction model of playback behavior which provides the accurate prediction of playback content in the future to ensure the smooth experience and optimize the distribution of resources. In order to balance the fast supplier discovery and low maintenance overhead, RACOM makes use of peer-centric overlay maintenance mechanism composed of the time window-based detection strategy and encounter-based synchronization strategy to reduce the maintenance overhead of reliable peers, obtain quasi real-time status of peers and support the mobility of mobile nodes. Simulation results show how RACOM achieves higher hit ratio, lower seek delay, lower server stress, lower peer load and less overlay maintenance overhead in comparison with another state of the art solution.     

A Theoretical Study on Modeling the Respiratory Tract With Ladder Networks by Means of Intrinsic Fractal Geometry

Fractional order modeling of biological systems has received significant interest in the research community. Since the fractal geometry is characterized by a recurrent structure, the self-similar branching arrangement of the airways makes the respiratory system an ideal candidate for the application of fractional calculus theory. To demonstrate the link between the recurrence of the respiratory tree and the appearance of a fractional-order model, we develop an anatomically consistent representation of the respiratory system. This model is capable of simulating the mechanical properties of the lungs and we compare the model output with in vivo measurements of the respiratory input impedance collected in 20 healthy subjects. This paper provides further proof of the underlying fractal geometry of the human lungs, and the consequent appearance of constant-phase behavior in the total respiratory impedance.      

Open corpus architecture for personalised ubiquitous e-learning

As the e-learning area matures, there are a growing number of e-learning content providers that produce and distribute material that covers a large range of topics, differs in quality and is represented in various formats. Lately, different devices and various network technologies allow extensive user access to educational content almost anywhere, anytime and from any device. Ubiquitous e-learning has the potential to provide continuous and context-based, educational material to human learners anytime, anywhere and on any device. Since each person has different expectations related to the content, the performance of the delivery and display of that content, it is desirable for an ubiquitous e-learning environment to provide user-oriented personalisation of e-learning material. However very often there are multiple sources of e-learning material at various web locations (open corpus resources) that cover the same topic, but differ in terms of quality, formatting and even cost. It is very difficult for learners to select the content that best suits their interests and goals, characteristics of the device used and delivery network as well as their cost budget. This paper proposes an innovative ubiquitous e-learning environment called Performance-based E-learning Adaptive Cost-efficient Open Corpus frameworK (PEACOCK) that provides support for the selection and distribution of personalised e-learning rich media content (e.g. multimedia, pictures, graphics and text) to e-learners such as it will best suit users’ interests and goals, meet their formatting preferences and cost constraints, while considering the limitations introduced by the end-user devices and the delivery networks to the user. PEACOCK’s main goal is to maximise the users’ e-learning experience and increase their learning satisfaction and learning outcome.     

Acylierung von Heterocyclen mit Kohlensäurederivaten. IV. Umsetzung von Benzoxazolin 2-thion mit Arylcyanaten. Kinetik und Mechanismus

Acylation of Heterocycles with Carbonic Acid Derivatives. IV. Reaction of Benzoxazolin-2-thione with Aryl Cyanates. Kinetics and Mechanism The arylcyanate benzoxazoline-2-thione ( 1 ) reaction in the presence and absence of the tertiary amines yields 1-aryloxyiminocarbonylbenzoxazoline-2-thione ( 2 ) and 2-thiocyanatobenzoxazole (4). A mechanism is proposed based on the influences of the reactants concentration, the concentration and basicity of tertiary amines, the solvent-water concentration, the arylcyanate substituents electronic effects on the reaction rate and the apparent activation parameters. This mechanism consists in the nucleophilic attack of the benzoxazoline-2-thione S-atom on the cyanate, followed by rearrangement through a four-center transition state.     

移动自组织网络下基于跨层感知和邻居协作的视频分享方案

Fast resources discovery and high Quality of Service (QoS) guarantee are the key det-erminants for efficient Mobile P2P (MP2P) video sharing. In this paper, we propose a Cross- Layer and One-Hop Neighbour-Assisted Video Sharing (CNVS) solution in Mobile Ad Hoc Networks (MANETs). By making use of cross- layer approaches to bridge the overlay and the MAC layer and with the help of dissemination assisted by one-hop neighbours, CNVS intel-ligently builds the resource-centric self-organ-ization node cluster group. In order to meet the QoS requirement, by making use of video resources access cost model, each peer can disconnect a less efficient connection with the original supplier and choose a peer that pro-vides a low access cost as the new supplier. Simulation results also show how CNVS achi-eves lower average end-to-end delay, less ave-rage number of hops for video data delivery, lower routing overhead and packet loss rate, and higher network throughput than another state-of-the-art solution.     

Genistein in 1:1 Inclusion Complexes with Ramified Cyclodextrins: Theoretical,Physicochemical and Biological Evaluation

Genistein is one of the most studied phytocompound in the class of isoflavones, presenting a notable estrogenic activity and in vitro and/or in vivo benefits in different types of cancer such as those of the bladder, kidney, lung, pancreatic, skin and endometrial cancer. A big inconvenience for drug development is low water solubility, which can be solved by using hydrophilic cyclodextrins. The aim of this study is to theoretically analyze, based on the interaction energy, the possibility of a complex formation between genistein (Gen) and three different ramified cyclodextrins (CD), using a 1:1 molar ratio Gen:CD. Theoretical data were correlated with a screening of both in vitro and in vivo activity. Proliferation of different human cancer cell lines, antimicrobial activity and angiogenesis behavior was analyzed in order to see if complexation has a beneficial effect for any of the above mentioned activities and if so, which of the three CDs is the most suitable for the incorporation of genistein, and which may lead to future improved pharmaceutical formulations. Results showed antiproliferative activity with different IC₅₀ values for all tested cell lines, remarkable antimicrobial activity on Bacillus subtilis and antiangiogenic activity as revealed by CAM assay. Differences regarding the intensity of the activity for pure and the three Gen complexes were noticed as explained in the text. The data represent a proof that the three CDs can be used for furtherer research towards practical use in the pharmaceutical and medical field.